Don't worry about logistics right now. Just write what comes to mind even if the idea scares you a little. We will work on the details later.
12 weeks is just long enough to achieve something amazing but not quite enough time to move a mountain:)
This should be something so easy you can get it done in 5-10 minues
This is probably the part of your project that will take the most time, effort, and intentionality.
Mail Invitations, find a location with a piano, tell my closest friends, etc...
Be specific and break big ideas down into tangible steps.
Remember, this is the point of no return. Once you do this it is 'go' time:)